Washington -- Sen. Dianne Feinstein ratcheted up pressure to pass her assault weapons bill against steep odds Wednesday, eliciting rawly emotional testimony from the weeping father of a 6-year-old boy who was slain at the elementary school massacre in Connecticut.

"I can still feel that hug, that pat on the back," Heslin said. His said his son told him, " 'Everything is going to be OK, Dad,' and it wasn't OK."

An emergency room physician on call that day, William Begg, used tissues handed to Heslin to wipe away his own tears. He said the bullets from the Bushmaster weapon are designed to explode in the body. Used on a child, he said, "that's not a survivable injury."

In calling a separate Judiciary Committee hearing on her bill after an earlier hearing centered on testimony from the National Rifle Association, Feinstein sought to demonstrate that mass shootings are increasing in frequency, police are in an arms race with criminals, and that limiting military-style weapons and high-capacity magazines would be constitutional.

Feinstein is hoping to revive a version of the 1994 assault weapons ban that was one of her biggest achievements when she was elected to the Senate two decades ago. The measure passed by a bare majority of one vote, before the filibuster requirement for a 60-vote threshold became routine in the Senate, and the law expired in 2004.

Committee Chairman Patrick Leahy, D-Vt., who has not endorsed Feinstein's bill, will include it as one of four pieces of gun control legislation he will introduce Thursday.

The other bills are designed to curb gun trafficking, bolster background checks and beef up school security. Feinstein's bill is the most controversial and could jeopardize support among several Democrats from Republican-leaning states, some of whom face re-election in two years, such as Mark Pryor of Arkansas.

Even if an assault weapons ban clears the Senate, it would probably die in the Republican-controlled House, where leaders oppose any such ban.

Feinstein's bill would ban 157 specific weapons, magazines that hold more than 10 rounds, and other weapons that have features such as a folding stock, pistol grip or detachable magazine that was developed for military weapons intended to kill people.

At Wednesday's hearing, Milwaukee Police Chief Edward Flynn continued speaking after Sen. Lindsey Graham, R-S.C., attempted to cut him off by insisting that current gun laws are poorly enforced.

"If you think we're going to do paperwork prosecutions, you're wrong," Flynn told Graham. Although opponents of the Feinstein bill argue the weapons are needed for self-defense, Flynn said the vast majority of "home-invasion victims" are drug dealers who do not need assault weapons.

Flynn said police are in an arms race with criminals, who are graduating from simple police revolvers to the military-style weapons criminals increasingly use, in what he called a "slow-motion mass murder" that is taking place daily in U.S. cities.

"How many people have to get murdered in a mass murder for it to be enough?" Flynn said. "Is 20 babies enough to say these implements should not be so easily distributed? That's what we're asking for."